12.1 Mole Ratios
12.1 Mole Ratios
Lesson Objectives
- Relate balanced chemical equations to everyday analogies, such as a recipe.
- Define stoichiometry.
- Use mole ratios to convert between amounts of substances in a chemical reaction.
Lesson Vocabulary
- mole ratio
- stoichiometry
Check Your Understanding
Recalling Prior Knowledge
- Why is it necessary to balance chemical equations?
- What do the coefficients of a balanced chemical equation represent?
Chemical equations are balanced in order to satisfy the law of conservation of mass. The mass of each element in a
chemical reaction must be conserved. A balanced equation is required for calculations that involve the quantities of
reactants used and products generated in a chemical reaction.
Everyday Stoichiometry
In the last chapter,Chemical Reactions, you learned about chemical equations and the techniques used to balance
them. Chemists use balanced equations to obtain quantitative information about chemical reactions. Before we look
at a chemical reaction, let’s reconsider the equation for the ideal ham sandwich.
As a reminder, our ham sandwich is composed of 2 slices of ham (H), 1 slice of cheese (C), 1 slice of tomato (T), 5
pickles (P), and 2 slices of bread (B). The equation for our sandwich is shown below:
2H + C + T + 5P + 2B→H 2 CTP 5 B 2Now let us suppose that you are having some friends over and need to make five ham sandwiches. How much of
each sandwich ingredient do you need? You would take the number of each ingredient required for one sandwich (its
coefficient in the above equation) and multiply by five. Using ham and cheese as examples and using a conversion
factor, we can write: